Over the past year, I've been in search of the best tv tuner card. After many purchases and returns later, I can tell you a bit about what I learned from my experiences.
First of all, Craig, I know what you are talking about. I had lockups too and at first I thought it was the 550pro card. But then after I updated the AGP driver for my motherboard, the problem went away. Also, make sure you get Cyberlink PowerCinema 4 and not 3. The PowerColor card at Newegg is now selling with version 4.
From months of frustration, I can tell you that if you want to transfer VHS tapes to DVD, the 550pro is definitely the best choice of anything available. It is the only card on the market that doesn't rely on a soundcard to encode the audio. You don't need to worry about audio/video sync problems that are prevalent on the majority of other analog cards.
The disadvantage of this card is that it is analog only.
If you want the best TV viewing experience on your computer, definitely take a close look at DViCO's Fusion5 Gold card. I use it for all my tv viewing: HDTV, ATSC TV, and NTSC (analog) TV. From all the products I have tried, it provides the best quality video (ATSC & NTSC) and allows you to watch unencrypted digital channels from your cable provider (locals in HD).
If you have never watched analog TV on your computer before, you will be in for a shock. You are accustomed to sharp, crisp images on a computer monitor and will be amazed by how blurry and fuzzy everything looks from an analog source. Once you start watching clean digital channels in HD, you will never want to go back.